What does this sentence mean (literature)

Its one specific phrase that is confusing me and its from Samuel Johnson's Preface to Shakespeare.
I bolded the exact words that are giving me problems and I also provided the sentences before and after to provide context. (I understand what he is saying wrt how Shakespeare mixes comedy and tragic, --its just that specific phrase "an appeal open from criticism to nature" that I don't get.

Johnson says:
"Almost all his plays are divided between serious and ludicrous characters, and, in the successive evolutions of the design, sometimes produce seriousness and sorrow, and sometimes levity and laughter. That this is a practice contrary to the rules of criticism will be readily allowed; but there is always an appeal open from criticism to nature. The end of writing is to instruct; the end of poetry is to instruct by pleasing.

So, I think he's using "appeal" in the second sense, and means that it is always possible to go to the higher court of 'Nature' to reverse a ruling by the lower court of 'Criticism'.

By the 'rules of criticism', you shouldn't weave back and forth between seriousness and levity in the same work. But that happens in Nature all the time, and the rules of Nature supercede the rules of criticism, so it's actually OK to go back and forth between seriousness and levity in the same work.

thanks much .. I think u nailed it, even though u said that's your take on it. I know what was confusing me now, it was the use of the court metaphor and also that "nature" (basically) = "real life" or maybe something like reality TV. ANyway, my completed sentence (ir ur interested) is "Even though Shakespeare's unorthodox methods often violate conventional rules of criticism, they don't violate real life, which is a superior measure of a plays worth".
The only part I'm unsure about now is the word "criticism" (if this should be the "rules of drama" or poetics or whatever Johnson means when he says "the ancients"
Thanks a lot for the fast help

I'd say 'nature' here is not supposed to mean 'real life' or natural world, but 'the nature of a (something)' - its purpose, or character.
So as the purpose of poetry is to instruct by pleasing, it is its nature to do so.

Taking it all together, the paraphrased passage would say: 'while such way of writing runs contrary to the standard rules of assessing literary works, in the end what counts is not whether something conforms to the rules, but whether it succeeds in achieving its intended purpose.'